This research is establishing an in vivo, physiologic experimental technique for determining material properties (the coefficients in the equation relating stress to strain) of a normal human cornea. The method uses available instruments for measuring corneal geometry (shape and thickness) and the internal pressure of the eye. Corneal shape, recorded with a photokeratometer before and during loading with a modified applanation tonometer, and corneal thickness, measured with a pachymeter, are combined with a finite element theory model to deduce material properties of a cornea. Knowledge of material properties 'of the cornea is significant in several areas of opthalmology. For example, how do differences in elastic properties of the cornea correlate with corneal pathologies like astigmatism, myopia, dystrophies, and keratoconus. More recently, radial keratotomy has been used as a surgical procedure for altering corneal curvature. Accurate measurements of Young's modulus would be valuable within the context of a mathematical model of the cornea for estimating the size and location of radial incisions in order to achieve a desired optical correction and would also give a basic understanding of what occurs to the structure of the corneal following this surgery.'